The present invention relates to a lens-fitted photo film unit with a protective cover which is movable between a closed position for covering a taking lens and an open position for uncovering the taking lens.
A lens-fitted photo film unit is widely known as a device, which is provided with a simple exposure mechanism and is loaded with an unexposed photo film cartridge in the factory, so that anyone can enjoy photography without bothering about loading and rewinding the film. Hereinafter, the lens-fitted photo film unit will be referred to as a film unit.
To improve the portability, the film unit has been made smaller and more compact. Also a film unit loaded with an IX240 type film cartridge that is smaller than a 135 type film cartridge has recently been produced and marketed. As containing the smaller IX240 type film cartridge, this film unit is designed to be smaller than that containing the 135 type film cartridge.
Indeed the small film unit is superior in portability, but the taking lens of the film unit tends to be stained as it is exposed all the time. Also, the photographer is more likely to touch the taking lens unconsciously. Accordingly, it is desirable to provide the film unit with a protective cover.
Japanese Utility Model Laid-open Application No. 60-60736 discloses a camera with a protective cover that is slidable between a closed position covering the taking lens and an open position uncovering the taking lens. The protective cover has an opening. When the protective cover is moved in the open position, the opening is placed in front of a flash projector, exposing the flash projector. Also, when the protective cover is moved in the open position, a flash charge switch is automatically turned on.
Since the flash charge switch is automatically turned off by moving the protective cover in the closed position, the camera of the above mentioned publication has an advantage of saving the batteries. However, as the flash charge switch is turned on whenever the protective cover moves in the open position, this camera is inconvenient when the flash photography is not wanted.
Because the film unit is so handy, the risk of accidentally pressing the shutter button and releasing the shutter unexpectedly is relatively high. In most cameras, each operation of the shutter button is detected by an electric switch, so that it is possible to provide a shutter release prevention device at a low cost by adding a circuit or a sequence that invalidates a detection signal from the electric switch when a lens protective cover is closed position. Such a circuit or sequence does not need remodeling or restructuring the camera. On the contrary, since the film unit uses a mechanical shutter, it is difficult to adopt such an electric shutter release prevention device.
As a protective cover for a taking lens, a cover that extends from a top edge to a bottom edge of the front side of the camera and slidable in a horizontal direction of the camera is popular. However, because the film unit has a bottom lid that is to be opened to remove a film cartridge having an exposed photo filmstrip rewound thereinto, if the film unit is provided with a horizontally slidable protective cover that extends to the front bottom edge of the film unit, it would be impossible to open the bottom lid.
Meanwhile, it is usual for cameras to use a decorative cover for reinforcing joints between parts of a camera housing, and covering up unnecessary openings or the like, as well as for decoration of the camera housing. On the contrary, it is difficult for the film unit to provide such a decorative cover in terms of cost and portability. Nevertheless, the wall thickness of the plastic unit housing of the film unit has been decreased for the sake of making the film unit smaller and cutting the material cost down.
Because the parts of the unit housing of the film unit are fastened to each other through snap-in engagements between resilient hooks and holes, the joints between the parts of the unit housing are getting weaker with the wall of the unit housing getting thinner. This is because the stiffness of the unit housing is lowered with the reduced wall thickness, so the unit housing easily gets twisted or distorted when a large load is applied to the film unit, e.g. when the film unit drops down. As a result of distortion, the snap-in engagement is broken up.
For the reasons as above, the film unit has conventionally been encased in a cardboard box, or wrapped with a cardboard sheet. However, with the conventional cardboard box and sheet, it is impossible to mount a protective cover that is slidable in front of the taking lens of the film unit.
On the other hand, the thickness of the film unit around the taking lens depends upon the focal length of the taking lens, and upon the diameter of the film cartridge on the side of the cartridge chamber. Therefore, in order to reduce the thickness of the film unit, it is conventional to use the front of the cartridge chamber as a grip and set back the other front area of the film unit from the grip. To provide a slidable protective cover, it is most reasonable to make the protective cover movable in the horizontal direction between the front of the taking lens and the front of the cartridge chamber. However, in the conventional film unit having a convex or protruding grip in front of the cartridge chamber, it is difficult to make the protective cover slidable. Even through it is possible to provide a slidable protective cover, it would certainly increase the thickness of the film unit housing.
In view of the foregoing, an object of the present invention is to provide a film unit with a protective cover that turns off a flash device of the film unit when the protective cover is closed, but allows the photographer to chose between the flash photography and the non-flash photography in the open position of the protective cover.
Another object of the present invention is to provide a film unit with a protective cover, wherein the shutter is prevented from being released when the protective cover is closed, by use of an inexpensive and simple mechanism.
A further object of the present invention is to provide a film unit with a protective cover that is slidable on the front of the film unit without interfering with a bottom lid for the removal of the exposed film cartridge.
Still another object of the present invention is to provide a film unit with a protective cover, wherein joints between the parts of the unit housing through snap-in engagements are reinforced without hindering the movement of the protective cover.
A further object of the present invention is to provide a film unit with a protective cover that is easy to mount, slidable smoothly without increasing the thickness of the film unit housing.
According to the present invention, a lens-fitted photo film unit having a flash unit incorporated therein is provided with a protective cover movable between a closed position covering a taking lens and an open position uncovering the taking lens; a flash charge switch manually operable between an ON position for starting charging a main capacitor of the flash unit and an OFF position for terminating charging the main capacitor; and a flash prevention device which prevents the flash charge switch from being moved to the ON position when the protective cover is in the closed position, allows the flash charge switch to be moved to the ON position when the protective cover is in the open position, and causes the flash charge switch to move to the OFF position in cooperation with the protective cover moving to the closed position when the flash charge switch is in the ON position. Since the flash prevention device prevents the flash charge switch from being moved to the ON position when the protective cover is in the closed position, it makes sure to avoid wasting batteries due to unnecessary charging operation. When the protective cover is in the open position, the flash prevention device just permits operating the flash charge switch to the ON position, so it is possible to choose a non-flash photography. Because the flash prevention device forcibly moves the flash charge switch to the OFF position as the protective cover is moved to the closed position when the flash charge switch is in the ON position, a waste of batteries by forgetting to turn off the flash charge switch is highly prevented.
Another lens-fitted photo film unit of the present invention is provided with a shutter button resiliently displaced upon a pressing operation; a shutter mechanism activated when the displacement of the shutter button is transmitted thereto; a protective cover movable between a closed position covering a taking lens and an open position uncovering the taking lens; and a shutter locking device which prevents the displacement of the shutter button from being transmitted to the shutter mechanism when the protective cover is in the closed position.
According to a preferred embodiment of the invention, a lens-fitted photo film unit is further provided with a pushing rod which is displaced together with the shutter button and transmits the displacement of the shutter button to the shutter mechanism; an opening formed through a front wall of the film unit in opposition to the pushing rod; and a locking member constituting the shutter locking device, wherein in the closed position of the protective cover the locking member moves through the opening in a locking position where the locking member prevents the displacement of the pushing rod, whereas in the open position of the protective cover the locking member moves in an unlocking position where the locking member allows the displacement of the pushing rod. According to this embodiment, the shutter locking device may be provided at a low cost with a simple construction by utilizing a conventional shutter mechanism that is released through a pushing rod and an opening that is needed for plastic forming the pushing rod.
The present invention also provides a lens-fitted photo film unit which has a cartridge chamber and a film roll chamber on opposite horizontal sides of a taking lens and a bottom lid at bottom of the cartridge chamber, wherein the bottom lid extends a little to a front portion of the film unit beyond a front bottom corner of the film unit; and a protective cover for opening and closing the taking lens has a vertical length that does not reach the front bottom corner of the film unit. So the protective cover is movable between a position in front of the taking lens and a position in front of the cartridge chamber without interfering with the bottom lid.
In a lens-fitted photo film unit having a unit housing which is constituted of at least two parts, including a front cover with a lens opening for exposing a taking lens and a rear cover, the present invention provides a protective cover movable in front of the front cover between a closed position covering the lens opening and an open position uncovering the lens opening; a first label stuck on a front surface of the protective cover; and a second label stuck on the unit housing across joints between the parts of the unit housing. To make the protective cover movable, two separate labels are used. Since one of the two labels covers the joints between the parts of the unit housing, the unit housing is reinforced.
In a lens-fitted photo film unit having a cartridge chamber and a film roll chamber on opposite horizontal sides of a taking lens, the present invention provides a protective cover slidable on a front surface of the film unit in a range between a position in front of the taking lens and a position in front of the cartridge chamber, wherein the front surface has a surface contour that is straight in the horizontal direction at least in the sliding range of the protective cover. According to this configuration, the surface the protective cover slides thereon is straight in the sliding direction, so the protective cover is easy to mount and operated smoothly. Moreover, an increase in thickness of the film unit involved by the provision of the protective cover may be reduced to the minimum.